Send email with Sendgrid (including template id and substitutions) with Laravel's notifications

ExampleNotification.php

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Notification;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Notifications\Messages\MailMessage;

//This example use the official's sendgrid php helper (https://github.com/sendgrid/sendgrid-php)
//You should install it before with composer require "sendgrid/sendgrid"

class ExampleNotification extends Notification
{
    use Queueable;

    public $api_key;
    public $sg;
    public $subs;
    public $template_id;
    public $to;
    public $from;
    public $subject;
    /**
     * Create a new notification instance.
     *
     * @return void
     */
    public function __construct( $data, $message )
    {
        $this->api_key = "Your Sendgrid Api Key";
        $this->sg = new \SendGrid($this->api_key);
        $this->data = $data;
        $this->message = $message;
        $this->from = "example@gmail.com";

        //select message configuration method based on the message name
        $this->selectMessage();
    }

    /**
     * Get the notification's delivery channels.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function via($notifiable)
    {
        //We should disable the automatic email provider from laravel
        // return ['mail'];
    }

    /**
     * Get the mail representation of the notification.
     *
     * @param  mixed  $notifiable
     * @return \Illuminate\Notifications\Messages\MailMessage
     */
    public function toMail($notifiable)
    {
        return (new MailMessage)
                    ->line('The introduction to the notification.')
                    ->action('Notification Action', 'https://laravel.com')
                    ->line('Thank you for using our application!');
        
    }

    /**
     * Get the array representation of the notification.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function toArray($notifiable)
    {
        return [
            //
        ];
    }
    
    /**
     * Handler for different messages or templates that you use in sendgrid
     *
     * @return void
     */
    private function selectMessage(){
        if( $this->message == "test_message")
            $this->testMessage();
    }

    /**
     * Test message's configuration
     *
     * @return void
     */
    private function testMessage(){
        $this->template_id = "your sendgrid template id";
        $this->to = $this->data->email;
        
        $this->subs = [
            "-yoursubcode-" => "Hello"
        ];
        $this->subject = "Your Subject";

        $this->sendTransactionEmail();
    }
    /**
     * Setup personalizations for sendgrind v3 mail
     *
     * @param \Sendgrid\Email Configured Email variable with the destination email
     *
     * @return \Sendgrid\Personalization Configured Personalizations for the mail 
     */
    private function personalizeEmail( $to ){

        $personalization = new \Sendgrid\Personalization();
        $personalization->addTo($to);
        foreach ($this->subs as $key => $value) {
            $personalization->addSubstitution( $key, (string) $value );    
        }
        

        return $personalization;
    }
    /**
     * Send the email via sendgrid 
     *
     * @return Object Http response from sendgrid
     */
    public function sendTransactionEmail(){
        
        $from = new \SendGrid\Email(null, $this->from);
        $to = new \SendGrid\Email(null, $this->to);
        
        //This should be at least 1 character even if it is empty
        $content = new \SendGrid\Content("text/html", " ");

        $mail = new \SendGrid\Mail($from, $this->subject, $to, $content);
        $mail->setTemplateId($this->template_id);
        
        $personalization = $this->personalizeEmail($to);
        $mail->addPersonalization($personalization);
        
        //Sending the email via sengrid api v3
        $response = $this->sg->client->mail()->send()->post($mail);
    }
}

//Example usage of a notifiable model class
//Remember to use use App\Notifications\ExampleNotification 
//in your controller or the class that you want to apply it
$user->notify(new ExampleNotification( $user, "test_message" ));